Numerous electronic devices use tuned circuits configured to operate at a resonant frequency. One well known configuration is referred to as a “tank circuit” and includes a capacitor and an inductor coupled in an electrically parallel arrangement. Each tank circuit is characterized by a resonant frequency that is a fixed value, unless one or both of the capacitive and inductive values are variable. Variability of the capacitor, inductor or both yields a variable frequency tank circuit.
Various forms of variable capacitor and variable inductor have been devised. However, classical known embodiments of such variable devices are too bulky, require mechanical adjustment, require continuous direct-current biasing or have other characteristics that render them undesirable for modern circuit design. Other known varieties of variable capacitor and variable inductor exhibit other unsuitable qualities. The present teachings address the foregoing concerns.